Use of polyaspartic acid amides as leather auxiliary products

ABSTRACT

Leather can be pretreated to obtain good body, soft feel, and excellent grain smoothness and solidity with products having a molecular weight of 700 to 30,000 and which are obtainable by reaction of 
     A. polysuccinimide having a molecular weight, determined as the number-average, of 500 to 10,000, with 
     B. 5 to 90 mol % based on the succinimide units of polysuccinimide A, and/or secondary amine, the nitrogen substituents of which contain 1 to 60 carbon atoms and which can be unsubstituted or substituted, at least 2.5 mol % of the nitrogen substituents of the amine containing at least 12 carbon atoms, 
     C. optionally, (i) derivatives of C 1  -C 18  -monocarboxylic acids, C 2  -C 10  -dicarboxylic acids, and/or (ii) monoisocyanates, diisocyanates epichlorohydrin (for reaction of amino and/or hydroxyl groups on the nitrogen substituents of the reaction product of A and B), and 
     D. 95 to 10 mol % of ring-opening base in the presence of water.

The invention relates to the use of products which can be obtained byreaction of polysuccinimide with amine as leather auxiliaries. The useof these auxiliaries leads to desirable properties, such as a good body,soft feel and excellent grain smoothness and solidity of grain.

Leathers of little body are thin and hard and have a low flexibility.With the aid of leather auxiliaries, attempts are made to achieve thedesired properties before, during and/or after tanning. It should beremembered here that, in spite of its softness, the leather should alsohave an adequate mechanical strength. Furthermore, the leather surfaceshould not be tacky; it should have a pleasant feel. Some auxiliariesresult in leathers which tend to have a loose grain; this undesirableconcomitant phenomenon should also be avoided.

Surprisingly, it has now been found that polyaspartic acid amides havethe excellent action described above on leather.

The invention thus relates to the use of products which have a molecularweight, determined as the number-average, of 700 to 30,000, preferably1300 to 16,000, and are obtainable by reaction of

A. polysuccinimide having a molecular weight, determined as thenumber-average, of 500 to 10,000, preferably 500 to 6000, in particular1000 to 4000, with

B. 5 to 90, preferably 20 to 80 mol %, based on the succinimide units ofpolysuccinimide A, of primary and/or secondary amine, the nitrogensubstituents of which contain 1 to 60, preferably 1 to 36, carbon atomsand can be substituted by fluorine atoms, hydroxyl groups, amino groupsand/or organosilicon radicals and/or interrupted by oxygen atoms, estergroups, amides groups, urea groups or urethane groups, at least 2.5,preferably at least 15, in particular at least 30 mol % of the nitrogensubstituents of the amine containing at least 12 carbon atoms, ifappropriate

C. (i) derivatives of C₁ -C₁₈ -monocarboxylic acids and/or C₂ -C₁₀-dicarboxylic acids and/or (ii) monoisocyanates, diisocyanates orepichlorohydrin (for reaction of amino and/or hydroxyl groups on thenitrogen substituents of the reaction product of A and B), and(necessarily)

D. 95 to 10, preferably 80 to 20 mol % of ring-opening base in thepresence of water,

as leather auxiliaries.

The polysuccinimide A used as the starting substance for thepolyaspartic acid amides to be used according to the invention is known.It can thus be prepared from aspartic acid water being split off; cf.,for example, J. Org. Chem. 26 (1961) 1084; FR 70 24 831; P. Neri in J.Med. Chem. 16 (1973), 893; U.S. Pat. No. 4,363,797.

Other processes start from maleic acid or its anhydride and ammonia(German Offenlegungsschrift 4 305 368; and U.S. Pat. No. 4,839,461).Thus, for example, polysuccinimide can be prepared by reaction of 80 to100 mol % of maleic acid and 20 to 0 mol % of succinic anhydride (as achain stopper) with ammonia at elevated temperature, in general at 85°to 240°, preferably 120° to 180° C., the water of reaction beingremoved.

U.S. Pat. No. 4,839,461 (=EP-A 256 366) describes the preparation frommaleic anhydride, water and ammonia. According to this process, maleicanhydride is converted into the monoammonium salt in an aqueous mediumwith the addition of concentrated ammonia solution. This maleic acidmonoammonium salt can be subjected to a thermal, optionally continuouspolycondensation, preferably at 150° to 180° C. in a reactor over aresidence time of 5 to 300 minutes, to give polysuccinimide.

The polysuccinimide A used as the starting compound can also be preparedby dehydration of polyaspartic acid.

The preparation of polyaspartic acid and its derivatives has been thesubject matter of numerous publications for a long time. The preparationcan thus be carried out by thermal polycondensation of aspartic acid (J.Org. Chem. 26, 1084 (1961); cf. also German Offenlegungsschrift 2 253190 and U.S. Pat. Nos. 4,696,981, 5,296,578 and 5,288,783.

In a preferred embodiment, polyaspartic acid essentially containsrecurring units of the following structures ##STR1##

In general, the proportion of the β-form is more than 50%, in particularmore than 70%, based on the sum of a+b.

In addition to the recurring aspartic acid units a) and b), it cancontain further recurring units, for example

c) malic acid units of the formula ##STR2## d) maleic acid units of theformula ##STR3## e) fumaric acid units of the formula ##STR4##

The polyaspartic acid can contain the "further" recurring units inamounts of up to 100% by weight, based on the sum of a+b.

Preferred polyaspartic acids have molecular weights, determined as theweight-average by gel permeation chromatography (calibrated withpolystyrene), of 500 to 10,000, preferably 1000 to 5000, in particular2000 to 4000.

The dehydration of polyaspartic acid to give polysuccinimide can becarried out at elevated temperature, preferably at 100° to 240° C., ifappropriate in the presence of a catalyst, for example in the presenceof 0.01 to 1% by weight, based on the polyaspartic acid, of an acidcatalyst, such as sulphuric acid, phosphoric acid or methanesulphonicacid.

Preferred amines B include secondary and--preferably--primary amines,such as, for example, monofunctional polyether-amines with a primary orsecondary amino group, such as α-methyl-ω-amino-polyoxyethylene,α-methyl-ω-aminopropyl-triethoxysilane, aminopropyl-trimethoxy-silane,aminopropyl-heptamethyl-trisiloxane,N-2-aminoethyl-aminopropyl-dimethyl-ethoxy-silane,N-2-aminoethyl-aminopropyl-methyl-dimethoxy-silane,perfluorohexyl-ethylamine,N-aminoethyl-N-methyl-perfluorooctylsulphonamide,N,N-dimethylethylenediamine, methylamine, diethylamine, butylamine,stearylamine, tallow fatty amine, oleylamine, undecylamine,dodecylamine, octylamine, hexylamine, eicosanylamine, hexadecylamine,2-ethyl-hexylamine, morpholine, ethanolamine, diethanolamine,bis-2-hydroxy-propylamine, bis-3-hydroxy-propylamine, 2- or3-hydroxypropylamine, ethoxy-ethylamine, ethoxy-ethoxy-ethylamine,butoxy-ethoxy-ethoxy-ethylamine, 2-methoxy-ethyl-amine,tetrahydrofurfurylamine, 5-aminopentanol, benzylamine,4-aminocyclohexylamine, taurine Na salt, glycine methyl ester,N-methylaminoethyl-sulphonic acid Na salt, dehydroabiethylamine,stearoyloxypropylamine, ##STR5##

The reaction of polysuccinimide with amines is known in principle; cf.,for example, German Offenlegungsschrift 2 253 190, EP-A 274 127, 406 623and 519 119, U.S. Pat. Nos. 3,846,380, 3,927,204 and 4,363,797; and P.Neri et al., Macromol. Syntheses 8, 25. Although the reaction can becarried out in excess amine B, it is preferably carried out in organicsolvents which are inert under the reaction conditions. Suitable suchsolvents are, for example, lactams, such as caprolactam,N-methylpyrrolidone and N-methylcaprolactam, polyalkylene diols andmono- and diethers thereof, such as ethylene glycol, diethylene glycol,triethylene glycol, ethylene glycol dimethyl and diethyl ether anddiethylene glycol monoethyl ether, as well as dimethylformamide anddimethylsulphoxide. The solvent content will as a rule not exceed 30% byweight, based on the total reaction mixture.

The reaction mixture can comprise water or paraffins, although this isnot preferred. The reaction is carried out in a temperature range from20° to 160° C., the reaction times being between 2 and 72 hours. Theproduct can be isolated by removal of the solvent by distillation or byprecipitation of the product in a non-solvent, such as acetone,methanol, ethanol, water or isopropanol, and, if desired, subsequentlydried.

The polyaspartic acid amides to be used according to the invention canbe prepared from the reaction product of A and B by opening theremaining incorporated succinimide rings. Possible ring-opening bases Dare both alkali metal hydroxides, carbonates and bicarbonates, inparticular sodium hydroxide and potassium hydroxide and sodiumcarbonate, and ammonia and amines - including the amines B.

According to a particular embodiment, maleic acid or maleic anhydrideand aqueous ammonia can be mixed in a molar ratio of 1:0.75 to 1:1.5 andwater can be distilled off. When the polysuccinimide has reached thedesired molecular weight, if appropriate co-using an organic solvent,such as diethylene glycol, pyrrolidone or N-methylpyrrolidone, amine Bis metered in and reacted at 130° to 160° C. A reaction time of 3 to 18,preferably 4 to 8 hours, is as a rule sufficient for the reaction withamine B. If appropriate, an organic solvent can be added. Thepolyaspartic acid amide to be used according to the invention is formeddirectly, and can easily be dispersed in water with simultaneous openingof the remaining incorporated succinimide rings with ring-opening baseD, the co-use of customary dispersing agents being advantageous.

In an idealized form, the polyaspartic acid amides to be used accordingto the invention contain recurring structural units of the formulae##STR6## or mixtures thereof with various substituents R¹ and R²##STR7## wherein R¹ and R² denote hydrogen or one of the radicalsdesignated above as nitrogen substituents, with the proviso that atleast one of the two radicals is other than hydrogen, and

M⁺ represents H⁺ or an alkali metal ion, an NH₄ ion or a primary,secondary or tertiary aliphatic ammonium radical, which preferablycarries at least one C₁ -C₂₂ -alkyl or -hydroxyalkyl group.

Suitable radicals M⁺ are, for example, hydroxyethylammonium,dihydroxyethylammonium, trishydroxyethylammonium, triethylammonium,ammonium butylammonium, benzyltrimethylammonium, morpholinium,stearylammonium and oleylammonium.

The polymer preferably contains the structural units I in an amount of 5to 90, in particular 20 to 80 mol %, based on all the recurring units.Preferred polyaspartic acid amides contain on average at least one C₁₂-C₂₄ -alkyl and/or -alkylene radical per structural unit I.

The polymer preferably contains the structural units II in an amount of95 to 10, in particular 80 to 20 mol %, based on all the recurringunits. Polyaspartic acid amides in which the carboxyl groups are presentin partly neutralized form are particularly preferred. The preferreddegree of neutralization is 10 to 70, preferably 20 to 50%. 0 to 20 mol% is the structure IIC based on the structures II.

The polymer contains the structural units III in an amount of 0 to 5 mol%, based on all the recurring units. Preferred polyaspartic acid amidescontain less than 1 mol % of the structural units III.

In the case where polysuccinimide A has been prepared from polyasparticacid which contains the abovementioned recurring units C), the carboxylgroups of these recurring units can also be amidated.

Suitable nitrogen substituents R¹ and R² include, independently of oneanother, for example, optionally hydroxyl-substituted C₁ -C₂₂ -alkyl orC₂ -C₂₂ -alkenyl groups from hydroxyethyl, hydroxypropyl, methyl, ethyl,butyl, hexyl, octyl, octenyl, decyl, undecyl, undecenyl, dodecyl,tetradecyl, hexadecyl, oleyl, octadecyl and 12-hydroxy-octadecenyl, C₅-C₁₀ -cycloalkyl radicals, such as cyclohexyl, C₁₂ -C₃₀ -radicalsinterrupted by oxygen atoms, ester groups, amide groups or urethanegroups, such as stearyloxyethyl, stearyloxyethoxyethyl andstearylcarbamoyloxyethyl, and radicals of the formulae ##STR8## whereinR⁶ and R⁶ denote C₁ -C₃₀ -alkyl, C₂ -C₃₀ -alkenyl or C₅ -C₁₀-cycloalkenyl,

R⁷ to R⁹ denote C₁ -C₄ -alkyl or -alkoxy and

M⁺ has the abovementioned meaning.

Nitrogen substituents which are interrupted by oxygen atoms, estergroups, amide groups or urethane groups can in principle be formedeither by using amines B already containing these groups or subsequentlyby reaction of initially introduced reactive nitrogen substituents withsuitable reaction partners.

Amide and ester groups can be introduced, for example, by subsequentconversion of already introduced aminoalkyl or hydroxyalkyl radicals byreaction with reactive carboxylic acid derivatives, preferably withderivatives of C₁ -C₁₈ -monocarboxylic acids or C₂ -C₁₀ -dicarboxylicacids, such as anhydrides or chlorides, for example acetic anhydride,acetylchloride, acryl and methacrylchloride, methacrylic anhydride,succinic anhydride, maleic anhydride, stearyl chloride or phthalicanhydride.

Urethane groups and urea groups can be introduced, for example, bysubsequent reaction of already introduced amino or hydroxyalkyl radicalswith mono- or diisocyanates, such as butyl isocyanate, stearylisocyanate, toluylene diisocyanate, isophorone diisocyanate or1-isocyanatomethyl-4-methyl-4-cyclohexyl isocyanate. Monoisocyanates areparticularly preferred. Crosslinked products are not preferred.

Nitrogen substituents interrupted by oxygen atoms are preferablyintroduced by using corresponding amino ethers B.

Epoxide groups can be introduced, for example, by subsequent epoxidationof already introduced alkenyl groups, for example with peracids. Anotherpossibility is alkylation with epichlorohydrin.

The polyaspartic acid amides to be used according to the invention arevery often self-dispersing, especially if the proportion of structuralunits I is less than 50 mol %. However, external dispersing agents canalso be used; possible such agents are in principle cationic, anionicand nonionic dispersing agents, such as are described, for example, in"Methoden der organischen Chemie " Methods of Organic Chemistry!(Houben-Weyl), 4th Edition, Volume XIV/1, George Thieme Verlag,Stuttgart 1961, page 190 et seq.

Preferred dispersing agents include, for example, C₈ -C₁₈ -n-alkylsulphates, C₈ -C₁₈ -n-alkyl-benezenesulphonates, C₈ -C₁₈-n-alkyl-trimethyl-ammonium salts, n-di-C₈ -C₁₈ -alkyl-dimethyl-ammoniumsalts, C₈ -C₁₈ -n-alkyl carboxylates, C₈ -C₁₈ -n-alkyl-dimethylamineoxides, C₈ -C₁₈ -n-alkyl-dimethylphosphine oxidesand--preferably--oligoethylene glycol mono-C₆ -C₁₈ -alkyl ethers havingon average 2 to 30 ethoxy groups per molecule. Some of the n-alkylradicals can also be replaced by unsaturated linear aliphatic radicals.Particularly preferred dispersing agents are oligoethylene glycolmono-C₁₀ -C₁₄ -alkyl ethers having on average 4 to 12 ethoxy groups permolecule, in particular oligoethylene glycol mono-C₁₂ -alkyl ethershaving on average 8 ethoxy groups per molecule.

Preferred dispersing agents furthermore include oleic acid, oleic acidsarcosides, ricinoleic acid, stearic acid, fatty acid partial esters ofpolyols, such as glycerol, trimethylolpropane or pentaerythritol, andacylation, ethoxylation and propoxylation products thereof, for exampleglycerol monostearate and monooleate, sorbitan monostearate andmonooleate, sorbitan tristearate and trioleate and reaction productsthereof with dicarboxylic acid anhydrides, such as succinic anhydride,maleic anhydride, phthalic anhydride or tetrahydrophthalic anhydride,and reaction products of bis-(hydroxymethyl)-tricyclodecane and maleicanhydride or succinic anhydride and derivatives thereof, preferably inthe form of their alkali metal or ammonium salts.

Particularly preferred dispersing agents are salts from long-chain fattyacids, preferably oleic acid, and an amino-alcohol, preferablyhydroxyethylamine, bishydroxyethylamine or trishydroxyethylamine.

The dispersion of the polyaspartic acid amides to be used according tothe invention can be formed by dispersing the polyaspartic acid amidesin an aqueous dispersing agent solution, preferably with heating totemperatures of 40° to 95° C. while stirring.

In general, it is advisable to disperse the polyaspartic acid amides tobe used according to the invention directly from the reaction mixture,which contains organic solvent, if appropriate, without intermediateisolation. Thus, for example, an aqueous dispersing agent solution canbe metered into the reaction mixture at temperatures of 70° to 130° C.,while stirring, so that a mixing temperature of 70° to 95° C. isestablished, and the organic solvent can be distilled off. Conversely,it is of course also possible for the reaction mixture to be dispersedin the aqueous dispersing agent solution or a mixture of the reactionmixture and dispersing agent to be dispersed in water. The removal ofthe solvent can also be omitted; in this case, however, the solventcontent of the dispersion should not exceed 10% by weight.

The dispersing agent content is in general not more than 30, preferably3 to 15% by weight based on the finished dispersion.

The solids content of the dispersions can be 5 to 70% by weight. Theaverage particle size of the dispersed polyaspartic acid amides is ingeneral 100 to 1000, preferably 100 to 700, and in particular 100 to 400nm.

To facilitate penetration of the auxiliaries into the leather, it may bedesirable to reduce the particle size of the disperse phase. For this,the pre-emulsion already obtained can be after-treated under a highshear gradient in known dispersing machines, such as in a jet disperseror mixers with the rotor-stator principle. The duration of thedispersing can be a few minutes up to 4 hours. The dispersing ispreferably carried out in a temperature range between 20° and 75° C.

The dispersions can be present in the form of pastes, especially atsolids contents above 40% by weight, but these can be readily dilutedwith water. The dispersions having a solids content below 40% by weightare present in the form of thinly liquid emulsions. The pH of theemulsions or pastes is between 4.5 and 12, preferably in the pH rangebetween 4.5 and 10.

The leather treatment can be carried out with an aqueous liquor whichcomprises the polyaspartic acid anhydrides to be used according to theinvention.

For this, the leather is brought into contact with the liquor byapplication by means of rolls or in a tank, preferably in a tanningdrum. After the treatment, the leather is dried.

The individual process steps are to be illustrated by the example of wetblue (chrome-tanned hides):

1. Neutralization of the chrome-tanned leather

2. Washing

3. Addition of the liquor comprising the polyaspartic acid amides to beused according to the invention

4. Reduction of the pH to pH values of <4.5, preferably to 3.0 to 4.5,by addition of carboxylic acid

5. Washing

6. Drying.

In a particular embodiment, leather can also be treated subsequentlywith a dispersion which comprises the polyaspartic acid amides to beused according to the invention.

Other auxiliaries can be co-used in the liquor which comprises theagents to be used according to the invention, or separately from this.These auxiliaries include: polymeric retanning substances based on knownpolyacrylate dispersions, leather dyestuffs, vegetable tannins, syntans,fat-liquoring agents, neutral oils and hydrophobizing agents. Only thosecombinations which are compatible with the dispersions of thepolyaspartic acid according to the invention can be used. The use ofadditives having an anionic charge as a rule presents no problems at aliquor pH of 6 to 4.5. However, these additives can also be employedparticularly advantageously before or after the use of the polyasparticacid amides to be used according to the invention.

Suitable fat-liquoring agents are, for example:

oxidized and/or sulphoxidized, preferably halogen-free C₁₆₋₃₀-hydrocarbons and/or C₃₂₋₁₀₀ -waxes,

C₂₋₅₄ -polycarboxylic acids partly esterified with C₈₋₃₀ -alcohols, suchas citric acid octadecyl ester and glutaric acid monooleate,

C₂₋₅₄ -polyols which are at least partly esterified with C₁₂₋₂₄ -fattyacids, such as sorbitan, glycerol, trimethylolpropane andpentaerythritol monostearate, monooleate, distearate, dioleate,monolaurate and the like.

Suitable syntans are, for example, the synthetic organic tannins knownto the expert (cf. K. Faber, "Gerbmittel, Gerbung und Nachgerbung "Tanning agents, tanning and retanning!, Frankfurt 1984).

Suitable vegetable tannins are, for example, chestnut extracts, mimosaand the like.

Fat liquoring plays an important role in the hydrophobizing action.Reference may be made to the literature in this context (cf. M.Hollstein "Entfetten, Fetten und Hydrophobieren bei derLederherstellung" Degreasing, fat liquoring and hydrophobizing inleather production!, Frankfurt, 1988; Ullmann's Encyclopadie dertechnischen Chemie Ullmann's Encyclopedia of Industrial Chemistry,keyword leather!.

Suitable neutral oils are, for example, animal and/or vegetable fats andoils, such as neat's foot oil, fish oil, sunflower oil, rape oil,coconut oil, palm kernel oil and soya oil, preferably non-halogenatedfatty acid esters, oleic acid methyl ester, paraffin oil and tallow.Suitable hydrophobizing agents are silicone emulsions and polymerdispersions containing perfluoroalkyl groups, including polyurethanescontaining perfluoroalkyl groups.

The polyaspartic acid amides to be used according to the invention alsoproduce a soft and full feel without further auxiliaries of theabovementioned categories. To fix the polyaspartic acid amides to beused according to the invention, it is sufficient to reduce the pH byaddition of a carboxylic acid. The liquor exhaustion is as a rule sogood that it is also possible to add the acid to the drum withoutdraining off the liquor. Preferred pH values should be less than 4.5 inorder to achieve adequate fixing in the leather. The range between 3.0and 4.5 is particularly preferred.

Instead of fixing with a carboxylic acid, fixing can also be carried outin the liquor by addition of polyvalent metal compounds, such as saltsor carboxylates or alkoxides of aluminium, titanium, zirconium orchromium. For ecological reasons, however, this is generally omitted.

To achieve an adequate action, according to the invention up to 10% byweight, preferably up to 7% by weight, of active substance, based on theshaped weight, is employed. The pH of the liquor at the start of thetreatment is preferably 5 to 7. If appropriate, the pH can be correctedby addition of bases, such as ammonia. The treatment is carried out at atemperature between 20 and 80° C., preferably between 35 and 60° C.After the treatment, a pH of about 4 to 6 is established in the liquor.The pH is reduced to 3 to 4.5 by addition of a carboxylic acid. Thepreferred carboxylic acid for the acidification is formic acid.

The use according to the invention of the polyaspartic acid amides givesleather having good hydrophobic properties.

If the hydrophobic action requirements are relatively high, it ispossible to carry out a concluding hydrophobization with silicone activecompounds or fluorocarbon resins. These active compounds are known tothe expert and can be metered into the same drum after a running time ofthe liquor of preferably 30 minutes. The active compounds, which areusually anionic, are readily compatible with the dispersions of thepolyaspartic acid amides to be used according to the invention.

Percentage data of the following examples in each case relate to theweight, unless stated otherwise; parts are parts by weight.

PREPARATION EXAMPLES

Preparation of the active compound with intermediate isolation

Example A 1

38.8 g of polysuccinimide having an average molecular weight of 3000 aredissolved in 374 g of dimethylformamide and the solution is heated to100°-110° C. with 86 g of stearylamine (0.80 mol/mol of imide). Themixture is stirred at this temperature for 5 hours. It is then cooled toroom temperature. The reaction mixture is poured into excess (1500 ml)methanol, the reaction product precipitating out in finely divided form.The product is filtered off over a suction filter and washed withmethanol and dried. A pale powder is obtained.

Example A 2

289 g of polysuccinimide having an average molecular weight of 3000 aredissolved in 1150 g of dimethylformamide and the solution is heated to110° C. with 400 g of stearylamine (0.5 mol/mol of imide). The mixtureis stirred at this temperature for 6 hours. It is then cooled to roomtemperature. The reaction mixture is poured into excess (6000 ml)methanol, the reaction product precipitating out in finely divided form.The product is filtered off over a suction filter and washed withmethanol and dried. A pale powder is obtained.

Example A 3

50 g of polysuccinimide having an average molecular weight of 6000 aredissolved in 250 g of dimethylformamide and the solution is heated to110°-120° C. with 110.8 g of stearylamine (0.80 mol/mol of imide). Themixture is stirred at this temperature for 5 hours. It is then cooled toroom temperature. The reaction mixture is poured into excess (2200 ml)methanol, the reaction product precipitating out in finely divided form.The product is filtered off over a suction filter and washed withmethanol and dried. A pale powder is obtained.

Example A 4

50 g of polysuccinimide having an average molecular weight of 3000 aredissolved in 200 g of dimethylformamide and the solution is heated to120° C. with 43 g of stearylamine (0.31 mol/mol of imide). The mixtureis stirred at this temperature for 6 hours. It is then cooled to roomtemperature. The reaction mixture is poured into excess (1000 ml)methanol, the reaction product precipitating out in finely divided form.The product is filtered off over a suction filter and washed withmethanol and dried. A pale powder is obtained.

Preparation of active compound without intermediate isolation

Example B 1

48.5 g of polysuccinimide having an average molecular weight of 3000 aredissolved in 40 g of N-methylpyrrolidone and the solution is heated to140° C. with 67.3 g of stearylamine (0.5 mol/mol of imide). The mixtureis stirred at this temperature for 6 hours. The resulting reactionmixture is further processed directly. If required, the product can becomminuted after cooling to room temperature.

Example B 2

48.5 g of polysuccinimide having an average molecular weight of 3000 aredissolved in 30 g of caprolactarn and the solution is heated to 140° C.with 67.3 g of stearylamine (0.5 mol/mol of imide). The mixture isstirred at this temperature for 6 hours. The resulting reaction mixtureis further processed directly. If required, the product can becomminuted after cooling to room temperature.

Example B 3

48.5 g of polysuccinimide having an average molecular weight of 3000 aredissolved in 40 g of N-methylpyrrolidone and the solution is heated to135°-145° C. with 74.85 g of stearylamine and 9.15 g of ethanolamine(0.86 mol of amines/mol of imide). The mixture is stirred at thistemperature for 6 hours. The resulting reaction mixture is furtherprocessed directly. If required, the product can be comminuted aftercooling to room temperature.

Example B 4

48.5 g of polysuccinimide having an average molecular weight of 3000 aredissolved in 40 g of N-methylpyrrolidone and the solution is heated to135°-145° C. with 74.85 g of stearylamine, 6.1 g of ethanolamine and 5.1g of N,N-dimethylaminopropylamine (0.86 mol of amines/mol of imide). Themixture is stirred at this temperature for 6 hours. The resultingreaction mixture is further processed directly. If required, the productcan be comminuted after cooling to room temperature.

Example B 5

32.3 g of polysuccinimide having an average molecular weight of 3000 aredissolved in 26.7 g of N-methylpyrrolidone and the solution is heated to140° C. with 44.6 g of oleylamine, (0.50 mol/mol of imide). The mixtureis stirred at this temperature for 6 hours. The resulting reactionmixture is further processed directly. If required, the product can becomminuted after cooling to room temperature.

Example B 6

146 g of polysuccinimide having an average molecular weight of 3000 aredissolved in 90 g of N-methylpyrrolidone and the solution is heated to130°-155° C. with 201.7 g of stearylamine, (0.50 mol/mol of imide). Themixture is stirred at this temperature for 8 hours. The resultingreaction mixture is further processed directly. If required, the productcan be comminuted after cooling to room temperature.

Preparation of the dispersions from polyaspartic acid amides A1 to A4(without an organic solvent)

Dispersion C 1

29.0 g of the product from Example A 1 are added to a solution which hasbeen heated to 75° C. and comprises 3.25 g of oleic acid, 1.97 g ofmonoethanolamine and 307.9 g of water. The dispersion is homogenized at75° C. for 30 minutes. The particle size of the disperse phase in thedispersion obtained by this procedure can be reduced by a jet disperserif it is not yet satisfactory. The particle size is then less than 500nm. The dispersion is adjusted to a solids content of 10% by weight.

Dispersion C 2

246.0 g of the product from Example A 2 are added to a solution whichhas been heated to 70° C. and comprises 24.6 g of oleic acid, 10.5 g ofmonoethanolamine and 1124.4 g of water. The dispersion is homogenized at70° C. for 30 minutes. The dispersion obtained by this procedure can beadjusted in its particle size by a jet disperser if it is not yetsatisfactory. The particle size is then 227 nm. The dispersion isadjusted to a solids content of 20% by weight.

Dispersion C 3

14.5 g of the product from Example A 3 are added to a solution which hasbeen heated to 70° C. and comprises 1.6 g of oleic acid, 0.98 g ofmonoethanolamine and 153.9 g of water. The dispersion is homogenized at70° C. for 30 minutes. The particle size is less than 500 nm. Thedispersion is adjusted to a solids content of 10% by weight.

Dispersion C 4

20.0 g of the product from Example A 4 are added to a solution which hasbeen heated to 70° C. and comprises 7.09 g of oleic acid, 0.86 g ofmonoethanolamine and 91.4 g of water. The dispersion is homogenized at70° C. for 30 minutes. The particle size is less than 400 nm. Thedispersion is adjusted to a solids content of 20% by weight.

Preparation of the dispersions from polyaspartic acid amides B1 to B6(with an organic solvent)

Dispersion D 1

50 g of the product from Example B 1 (corresponding to 37.17 g of activecompound) are initially introduced into the preparation vessel at 110°C. A solution of 3.7 g of oleic acid and 1.6 g of monoethanolamine in156.9 g of water is added dropwise at this temperature. After additionof the total amount, the mixture is first homogenized at 90° C. in thecourse of 30 minutes. The dispersion obtained by this procedure can beadjusted in its particle size by a jet disperser if it still containscoarse particles. Even without this dispersing technique, the emulsionhas a particle size<500 nm. The dispersion is adjusted to a solidscontent of 20% by weight.

Dispersion D 2

50 g of the product from Example B 2 (corresponding to 39.71 g of activecompound) are initially introduced into the preparation vessel at 110°C. A solution of 3.97 g of oleic acid and 1.69 g of monoethanolamine in172.6 g of water is added dropwise at this temperature. After additionof the total amount, the mixture is first homogenized at 70° C. in thecourse of 60 minutes. The dispersion obtained by this procedure can beadjusted in its particle size by a jet disperser if it still containscoarse particles. Even without this dispersing technique, the emulsionhas a particle size<500 nm. The dispersion is adjusted to a solidscontent of 20% by weight.

Dispersion D 3

50 g of the product from Example B 3 (corresponding to 38.41 g of activecompound) are initially introduced into the preparation vessel at 110°C. A solution of 3.7 g of oleic acid and 1.70 g of monoethanolamine in242.7 g of water is added dropwise at this temperature. After additionof the total amount, the mixture is first homogenized at 80° C. in thecourse of 240 minutes. The dispersion obtained by this procedure can beadjusted in its particle size by a jet disperser if it still containscoarse particles. Even without this dispersing technique, the emulsionhas a particle size<500 nm. The dispersion is adjusted to a solidscontent of 14.7% by weight.

Dispersion D 4

50 g of the product from Example B 4 (corresponding to 38.54 g of activecompound) are initially introduced into the preparation vessel at 110°C. A solution of 3.7 g of oleic acid and 1.70 g of monoethanolamine in242.7 g of water is added dropwise at this temperature. After additionof the total amount, the mixture is first homogenized at 80° C. in thecourse of 120 minutes. The dispersion obtained by this procedure can beadjusted in its particle size by a jet disperser if it still containscoarse particles. Even without this dispersing technique, the emulsionhas a particle size<500 nm. The dispersion is adjusted to a solidscontent of 14.7% by weight.

Dispersion D 5

50 g of the product from Example B 5 (corresponding to 37.12 g of activecompound) are initially introduced into the preparation vessel at 110°C. A solution of 3.7 g of oleic acid and 1.6 g of monoethanolamine in156.9 g of water is added dropwise at this temperature. After additionof the total amount, the mixture is first homogenized at 70° C. in thecourse of 180 minutes. The dispersion obtained by this procedure can beadjusted in its particle size by a jet disperser if it still containscoarse particles. Even without this dispersing technique, the emulsionhas a particle size<500 nm. The dispersion is adjusted to a solidscontent of 20% by weight.

Dispersion D 6

50 g of the product from Example B 6 (corresponding to 39.71 g of activecompound) are initially introduced into the preparation vessel at 110°C. A solution of 5.2 g of monoethanolamine in 169.3 g of water (withoutoleic acid) is added dropwise at this temperature. After addition of thetotal amount, the mixture is first homogenized at 80°-90° C. in thecourse of 180 minutes. The dispersion obtained by this procedure can beadjusted in its particle size by a jet disperser if it still containscoarse particles. Even without this dispersing technique, the emulsionhas a particle size 347 nm. The dispersion is adjusted to a solidscontent of 20% by weight.

Dispersion D 7

10 g of the product from Example B 1 (corresponding to 7.43 g of activecompound) are initially introduced into the preparation vessel at 110°C. A solution of 0.74 g of an emulsifier which has been obtained byreacting 1 mol of trimethanolpropane monostearate with 2 mol of succinicanhydride in bulk and 0.32 g of monoethanolamine in 31.4 g of water isadded dropwise at this temperature. After addition of the total amount,the mixture is initially homogenized at 70° C. in the course of 180minutes. The dispersion obtained by this procedure can be adjusted inits particle size by a jet disperser if it still contains coarseparticles. Even without this dispersing technique, the emulsion has aparticle size<500 nm. The dispersion is adjusted to a solids content of20% by weight.

Dispersion D 8

10 g of the product from Example B 1 (corresponding to 7.43 g of activecompound) are initially introduced into the preparation vessel at 110°C. A solution of 0.74 g of an emulsifier which has been obtained byreacting 1 mol of glycerol monostearate with 2 mol of succinic anhydridein bulk and 0.32 g of monoethanolamine in 31.4 g of water is addeddropwise at this temperature. After addition of the total amount, themixture is initially homogenized at 70° C. in the course of 180 minutes.The dispersion obtained by this procedure can be adjusted in itsparticle size by a jet disperser if it still contains coarse particles.Even without this dispersing technique, the emulsion has a particlesize<500 nm. The dispersion is adjusted to a solids content of 20% byweight.

Use Examples: leather treatment

The following auxiliaries, inter alia, were employed:

®TANIGAN PAK-N: light-fast anionic retanning substance with aneutralizing and buffer action, condensation product of aromaticsulphonic acids. pH 6.6, concentration about 95%, product of Bayer AG,Leverkusen

®TANIGAN QF: Synthetic replacement tannin for after-treatment of chromeleather, pH 5.3, acid number 0 to 5, concentration about 96%, product ofBayer AG, Leverkusen

®CROMOSAL B: Basic chrome tannin having a Cr₂ O₃ content of 26%.

The dispersions from Examples C and D were tested as leatherauxiliaries. The following recipe is suitable for upper leather.

Material: chrome-tanned cow wet blue, grain leather, contains 2.5% ofCr₂ O₃

Shaped thickness: 2 mm

The following percentage data are based on the shaped weight. Theamounts of the auxiliaries employed in the following recipe are based onthe active compound available.

    ______________________________________    Neutralization              50% water, 40° C.              +2% ®TANIGAN PAK-N                                  45     minutes              +0.5% sodium bicarbonate              pH of the liquor at the end: 5.1 to 5.3              drain off liquor    Dyeing    100% water, 50° C.              +1% ®BAYGENAL Braun CGG                                  20     minutes    Retanning +4% ®TANIGAN QF 150    minutes              Replacement tannin (pH about 5.3)              +8% chestnut, sweet              pH of the liquor at the end: 4.3 to 4.4              drain off the liquor    Washing   200% water, 50° C.                                  10     minutes              drain off the liquor    Hydrophobization              100% water, 50° C.              +0.5% NH.sub.4 OH   20     minutes              +6.5% dry substance 60     minutes              product according to the invention              from Example C 4              pH of the liquor at the end: 4.9 to 5.0              drain off the liquor    Fixing    50% water, 30° C.              for a) +0.5% HCOOH (in 2 portions)                                  a 10   min.              for b) +2.5% ®CHROMOSAL B                                  60     minutes              pH of the liquor at the end 3.9              drain off the liquor (clear              and colourless).    ______________________________________

Rinse, lay the leather on a buck overnight, sammy. Vacuum drying (10minutes at 70° C.), condition in air, stake.

Soft solid-grain leathers with a pleasantly full feel were obtained. Thegrain side was very smooth. The uptake of water by the leather producedby the process described above was less than 60% after 24 hours. In aMaeser penetrometer, more than 1000 folds were achieved before waterpenetrated.

Further use examples are shown in Table 1. A simplified procedure waschosen here, the working steps of dyeing and retanning being omitted inorder to detect possible discolorations. For better differentiation ofthe products according to Examples C and D. the use of only 2.5% ofactive compound was chosen. By using amounts of 6.5%, water uptakevalues of less than 60% can be established, as the recipe describedabove shows by way of example.

                  TABLE 1    ______________________________________    Properties of the leathers    Dispersion according to    Grain smoothness    Example No.      Feel rating*                               rating**    ______________________________________    C1               2         1    C2               1         1    C3               3         1    C4               1         1    D1               2         1    D2               2         1    D3               2         2    D4               2         2    D5               1         2    D6               2         1    D7               2         1    D8               2         1    Comparison (Lubritan WP.sup.+)                     3         2    ______________________________________     *Rating 1 = soft, rating 5 = hard     **Rating 1 = smooth, rating 5 = rough     .sup.+ Commercial product of Rohm & Haas, testing likewise according to     the use instructions given above.

We claim:
 1. A method for treating leather comprising treating leatherwith leather auxiliary products having a molecular weight, determined asthe number-average, of 700 to 30,000 prepared by reaction ofA.polysuccinimide having a molecular weight, determined as thenumber-average, of 500 to 10,000 and comprising succinimide units, withB. 5 to 90 mol %, based on the succinimide units of polysuccinimide A,of at least one primary or secondary amine, wherein the nitrogen of theamine is substituted with substituents containing 1 to 60 carbon atomswhich can be unsubstituted or substituted by at least one of fluorineatoms, hydroxyl groups, amino groups, or organosilicon radicals, andwhich substituents can be uninterrupted or interrupted with at least oneof ester groups, amides groups, urea groups, urethane groups, or oxygenatoms, at least 2.5 mol % of the substituents on the nitrogen of theamine containing at least 12 carbon atoms, C. optionally, at least oneof (i) derivatives of C₁ -C₁₈ -monocarboxylic acids, or C₂ -C₁₀-dicarboxylic acids, or at least one of (ii) monoisocyanates,diisocyanates or epichlorohydrin, and D. 95 to 10 mol %, based on thesuccinimide units, of ring-opening base in the presence of water.
 2. Amethod according to claim 1, in which the leather auxiliary productshave a molecular weight, determined as the number-average, of 1300 to16,000.
 3. A method according to claim 1, in which the amount of amine Branges from 20 to 80 mol % and the amount of ring-opening base D rangesfrom 80 to 20 mol %.
 4. A method according to claim 1, in which thenitrogen substituents of amine B have 1 to 30 carbon atoms.
 5. A methodaccording to claim 1, in which the leather is treated with an aqueousdispersion of the leather auxiliary products.
 6. A method according toclaim 5, in which the leather auxiliary products are fixed on theleather by using a pH of 3.2 to 4.5.
 7. A method according to claim 5,in which the products are fixed on the leather by addition of compoundsof chromium, aluminium, titanium or zirconium.
 8. A method according toclaim 1, in which the molecular weight of the polysuccinimide A is 500to
 6000. 9. A method according to claim 1, in which the molecular weightof the polysuccinimide A is 500 to
 1000. 10. A method according to claim1, in which the amount of said amine B is from 20 to 80 mol %.
 11. Amethod according to claim 1, in which at least 15 mol % of the nitrogensubstituents of amine B contains at least 12 carbon atoms.
 12. Leatherswhich have been treated in accordance with the method of claim 1.